Magnetic Circuit MCQs with Explanations

Hysteresis loss occurs in a magnetic material due to the lagging of flux density (B) behind the magnetizing force (H) when the material undergoes cyclic magnetization. This delay in response leads to energy dissipation in the form of heat , which is represented by the area enclosed by the hysteresis loop . Why Not the Other Options? Option A: Rapid reversals of its magnetization – This contributes to hysteresis loss but is not the root cause . The loss happens due to the delay in realigning the magnetic domains, not just the rapid changes themselves. Option C: Molecular friction – This is a misleading term . While there is internal resistance in domain movement, hysteresis loss is primarily due to flux lag rather than physical friction at the molecular level. Option D: Its high retentivity – Retentivity refers to a material’s ability to retain magnetization after the external field is removed. A material with high retentivity does not necessarily have high hysteresis loss . Retentivity influences the shape of the hysteresis loop but is not the direct cause of hysteresis loss . Thus, Option B is the correct answer.

A ferrite core has less eddy current loss than an iron core because ferrites have high resistance . Eddy currents are circulating currents that are induced in a conducting material (like a core) when it is exposed to a changing magnetic field. These currents lead to energy loss in the form of heat due to the electrical resistance of the material. Ferrite cores are made from materials that have high electrical resistance, which means they offer more opposition to the flow of eddy currents. As a result, the eddy current losses in ferrite cores are significantly lower compared to materials with lower resistance, like iron cores. This property makes ferrite cores suitable for applications in high-frequency transformers and other electronic devices where minimizing energy losses is important.

Current is the correct answer to “While comparing magnetic and electric circuits, the flux of magnetic circuit is compared with which parameter of electrical circuit”. This question is standard in competitive examination syllabi for Magnetic Circuit.

Lowers their power efficiency is the correct answer to “Point out the wrong statement. Magnetic leakage is undesirable in electric machines because it”. This question is standard in competitive examination syllabi for Magnetic Circuit.

Weber is the correct answer to “The unit of magnetic flux is”. This question is standard in competitive examination syllabi for Magnetic Circuit.

Eddy current loss is the correct answer to “Laminated cores, in electrical machines, are used to reduce”. This question is standard in competitive examination syllabi for Magnetic Circuit.

High, high is the correct answer to “Those materials are well suited for making permanent magnets which have ________ retentivity and ________ coercivity.”. This question is standard in competitive examination syllabi for Magnetic Circuit.

High, low is the correct answer to “Those magnetic materials are best suited for making armature and transformer cores which have ________permeability and _________hysteresis loss.”. This question is standard in competitive examination syllabi for Magnetic Circuit.

20 is the correct answer to “The initial rate of rise of current through a coil of inductance 10 H when suddenly connected to a D.C. supply of 200 V is ___________Vs”. This question is standard in competitive examination syllabi for Magnetic Circuit.

1 is the correct answer to “Relative permeability of vacuum is”. This question is standard in competitive examination syllabi for Magnetic Circuit.

Conductivity is the correct answer to “Permeability in a magnetic circuit corresponds to_________ in an electric circuit.”. This question is standard in competitive examination syllabi for Magnetic Circuit.

Permeance is the correct answer to “Conductance is analogous to”. This question is standard in competitive examination syllabi for Magnetic Circuit.

Alnico alloys is the correct answer to “Permanent magnets are normally made of”. This question is standard in competitive examination syllabi for Magnetic Circuit.

High retentivity is the correct answer to “A material for good magnetic memory should have”. This question is standard in competitive examination syllabi for Magnetic Circuit.

Permeance is the correct answer to “Reciprocal of reluctance is”. This question is standard in competitive examination syllabi for Magnetic Circuit.

Time constant remains unchanged is the correct answer to “When both the inductance and resistance of a coil are doubled the value of”. This question is standard in competitive examination syllabi for Magnetic Circuit.

Low hysteresis loss is the correct answer to “Silicon steel is used in electrical machines because it has”. This question is standard in competitive examination syllabi for Magnetic Circuit.

Large is the correct answer to “If the area of hysteresis loop of a material is large, the hysteresis loss in this material will be”. This question is standard in competitive examination syllabi for Magnetic Circuit.

Weber/sq. m is the correct answer to “The unit of retentivity is”. This question is standard in competitive examination syllabi for Magnetic Circuit.

Prevent saturation is the correct answer to “An air gap is usually inserted in magnetic circuits to”. This question is standard in competitive examination syllabi for Magnetic Circuit.

More than 100 or 1000 is the correct answer to “The relative permeability of a ferromagnetic material is”. This question is standard in competitive examination syllabi for Magnetic Circuit.

41.4 is the correct answer to “Energy stored by a coil is doubled when its current is increased by percent.”. This question is standard in competitive examination syllabi for Magnetic Circuit.

It has good residual magnetism is the correct answer to “Hard steel is suitable for making permanent magnets because”. This question is standard in competitive examination syllabi for Magnetic Circuit.

$$\frac{1}{{{\text{Henry}}}}$$ is the correct answer to “The unit of reluctance is”. This question is standard in competitive examination syllabi for Magnetic Circuit.

Ambient temperature is the correct answer to “Hysteresis loss least depends on”. This question is standard in competitive examination syllabi for Magnetic Circuit.

At the start of the current flow is the correct answer to “The rate of rise of current through an inductive coil is maximum”. This question is standard in competitive examination syllabi for Magnetic Circuit.

Reluctance is the correct answer to “The property of a material which opposes the creation of magnetic flux in it is known as”. This question is standard in competitive examination syllabi for Magnetic Circuit.

Permeability is the correct answer to “Conductivity is analogous to”. This question is standard in competitive examination syllabi for Magnetic Circuit.